The relationship between energy and matter is described by Einstein's theory of special relativity. This theory suggests that matter can be converted into energy and energy into matter. This relationship can best be demonstrated by observing the effects of ionizing radiation on bulk material. Ionizing radiation consists of a flux of particles or photons with sufficient energy to break up molecules or to detach electrons from atoms upon impact. At the moment of impact, electromagnetic energy (photons) is converted into mass (e.g., Compton electrons, secondary electrons, etc.). Similarly, mass in the form of energetic particles (e.g., electrons, neutrons, alpha particles, etc.) is attenuated to produce secondary electromagnetic energy, such as bremsstrahlung (radiation emitted by an electron accelerated in its collision with the nucleus of an atom, "braking radiation"). Therefore, as a steady flux of ionizing radiation passes through bulk material, it produces a dynamic condition where energy is converted into matter and matter into energy.
Radioisotopic decay, such as alpha decay or beta decay, generates charged particles. The movement of these charged particles therefore produces an electric current. Attempts have been made to convert the movement of these charged particles directly into electrical energy. However, directly producing electrical energy from radioisotopic decay has had numerous problems.
The first problem encountered is that the charged particles emitted during the decay contain a broad spectrum of energy levels. For example, in beta decay, a beta particle (.beta..sup.- or .sub.-1 .epsilon..sup.0) is emitted. However, the emitted .beta. particles or electrons are not mono-energetic. Rather, there is a distribution of electron energies from zero up to the maximum energy of 13.4 MeV. A design directed at a particular energy level would lose lower energy level electrons because these electrons would have insufficient energy to get to the collector. Similarly, much higher energy level electrons would collide with the collector, generating heat, and attenuation into another energy level, resulting in losses as well. Such devices are typically high voltage, low current devices.
A second problem frequently encountered was leakage current losses. The leakage current occurred when higher energy electrons collide with the collector and would then be ejected out the back side of the collector. Additionally, leakage occurred through bremsstrahlung or "braking radiation." Bremsstrahlung radiation is produced in a collision between an electron and a positively charged nucleus. In order to prevent losses due to bremsstrahlung, very thick electron collectors were used which were very heavy and dense. As a result, only one or two plates could be used, so it was not possible to collect at a multiple of electron energy levels. Finally, leakage also occurred through back scattering, where the electromagnetic energy and the particles are back scattered 180.degree. from a forward direction.
The efficiencies of and energy levels produced by prior designs were also quite low. These designs typically used one emitter electrode and one collector electrode. Therefore, when the energy was drawn off the collector electrode, it dropped in potential. The resulting drop in potential produces an "off time" while the potential builds back up on the collector electrode to the desired energy level. Once the desired collector energy level is achieved, the collection is done and the collector again drops in potential. This "off time" for collection resulted in low efficiency, and low total energy available.
Accordingly, prior to the development of the present invention, there was no device for the direct conversion of ionizing radiation into electrical energy which effectively converts charged particles from a multitude of energy levels, recovering some of the energy produced through back scattering and bremsstrahlung. Additionally, prior to the development of the present invention, there was no device which provided for a continuous potential on the collector electrode to preclude inefficiencies due to low collector potential.